Our long-term goal is to discover calpain inhibitors as potential treatment for heart attack and stroke. Heart disease and stroke are major causes of mortality and morbidity in the United States. New drugs with novel mechanisms of action are needed for the management of these conditions. Mounting evidence suggests that an episode of cardiac ischemia (heart attack) or cerebral ischemia (stroke) initiates a chain of biochemical events that activate calpain. Activated calpain degrades structural proteins resulting in cell death. Calpain is therefore considered an attractive pharmacologic target for intervention in heart attack and stroke. We have discovered potent and selective inhibitors of calpain. Considering that most of the reported calpain inhibitors are not selective for the enzyme our new inhibitors are of interest. However, we have not been able to evaluate the cardioprotection effect of the inhibitors because of their poor water-solubility and metabolic instability of a pharmacophoric aldehyde group. We are therefore proposing to synthesize analogues of our new inhibitors in which the oxidizable aldehyde group is masked as the hemiacetal or replaced with non- oxidizable functional groups such as the alpha-ketoamide and alpha-ketohydrazide. These groups will be incorporated as isosteric pharmacophoric replacement for the oxidizable aldehyde. We will also incorporate ionizable groups to enhance water solubility of the inhibitors. The changes will allow evaluation of the inhibitors as cardioprotectants. Thus, the central hypothesis to be investigated is: "water-soluble and metabolically stable derivatives of our novel potent and selective calpain inhibitors are cardioprotective." The Specific aims are: (1) to use an iterative approach of structure-based molecular design, synthesis, and enzymological evaluation to develop potent, selective, water-soluble, cell permeable and metabolically stable analogues of our new calpain inhibitors; (2) to characterize the cardioprotection effectiveness of three of the best inhibitors that will be developed in specific aim #1 using the rat isolated heart model of global ischemia. Achievement these aims will afford new calpain inhibitors with desirable physicochemical properties as biomedical tools for studying calpain function in laboratory animals and as drug leads for the discovery of novel therapies for treating heart attack and stroke. Furthermore, the proposed studies will provide mechanistic insight into the mode of action of calpain inhibitors as cardioprotectants.